Prediction of Risk Factors for Pathological Fracture After Bone Tumor Biopsy Using Finite Element Analysis

Abstract

Purpose: We aimed to determine if finite element analysis (FEA) provides useful thresholds for bone biopsy practice patterns.

Methods: The femoral head compression test was performed on rabbit femurs, using FEA to identify the part of the bone that preferentially fractures (n=15/group). Four types of rectangular biopsy holes were made using finite element (FE) models. These models were divided into control (no defect), defect 1 (10% width), defect 2 (20% width), defect 3 (30% width), and defect 4 (40% width) groups (n=15 each). Three types of rectangular biopsy holes (defect A, 27% length; defect B, 40% length; defect C, 53% length) were also made using FE models (n=15 each). The load to failure was then predicted using FEA.

Results: Almost all femurs with no defect were fractured at the femoral shaft in both the femoral head compression test and FEA. The experimental load to failure in intact femurs was predicted well by the FE models (R²=0.74, p<0.001). There was also a strong linear correlation of stiffness between compression test in femurs with no defect and the FEA (R²=0.68, p<0.001). Therefore, the femoral shaft was targeted for FEA. The median predicted loads by FEA were significantly higher for defect 1 than for the other types when testing the widths of the rectangular defects, but there were no significant differences among the three types when testing for defect length.

Conclusion: The FEA results correlated well with those of the femoral head compression test. A width <10% of the circumference length in bone biopsy holes helps minimize bone strength reduction using FEA. It may be useful for orthopedic doctors to perform FEA to avoid pathological fractures after bone tumor biopsy.

Keywords: New Zealand white rabbits; bone tumor biopsy; femur; finite element analysis; orthopedics.